If your Mac has a Touch Bar, you can use the Touch Bar to interact with Horizon Client.

You can use the Touch bar to add a new server and disconnect from a server. After you are connected to a remote desktop, you can use the Touch Bar to disconnect, log off, restart, and reset the desktop, send Ctrl+Alt+Delete to the desktop, enter and exit full-screen mode, and bring the desktop and application selection window to the foreground. The logoff, reset, and restart features are available only if an administrator enables them.

The Touch Bar feature does not support remote application windows. You cannot use the Touch bar to enter and exit full-screen mode or bring the desktop and application selection window to the foreground if the remote desktop is in exclusive mode.